A biogeographic realm is the broadest biogeographic division of Earth's land surface, based on distributional patterns of terrestrial organisms. They are subdivided into bioregions, which are further subdivided into

ecoregion An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...

s. A biogeographic realm is also known as "ecozone", although that term may also refer to ecoregions.

Description

The realms delineate large areas of Earth's surface within which organisms have evolved in relative isolation over long periods of time, separated by geographic features, such as

ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...

s, broad

desert A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...

s, or high

mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have aris ...

s, that constitute natural barriers to migration. As such, biogeographic realm designations are used to indicate general groupings of organisms based on their shared biogeography. Biogeographic realms correspond to the floristic kingdoms of

botany Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

or zoogeographic regions of

zoology Zoology ( , ) is the scientific study of animals. Its studies include the anatomy, structure, embryology, Biological classification, classification, Ethology, habits, and distribution of all animals, both living and extinction, extinct, and ...

. From 1872, Alfred Russel Wallace developed a system of zoogeographic regions, extending the

ornithologist Ornithology, from Ancient Greek ὄρνις (''órnis''), meaning "bird", and -logy from λόγος (''lógos''), meaning "study", is a branch of zoology dedicated to the study of birds. Several aspects of ornithology differ from related discip ...

Philip Sclater Philip Lutley Sclater (4 November 1829 – 27 June 1913) was an England, English lawyer and zoologist. In zoology, he was an expert ornithologist, and identified the main zoogeographic regions of the world. He was Secretary of the Zoological ...

's system of six regions. Biogeographic realms are characterized by the evolutionary history of the organisms they contain. They are distinct from

biome A biome () is a distinct geographical region with specific climate, vegetation, and animal life. It consists of a biological community that has formed in response to its physical environment and regional climate. In 1935, Tansley added the ...

s, also known as major habitat types, which are divisions of the Earth's surface based on ''life form'', or the adaptation of animals, fungi, micro-organisms and plants to climatic,

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

, and other conditions. Biomes are characterized by similar climax vegetation. Each realm may include a number of different biomes. A tropical moist broadleaf forest in Central America, for example, may be similar to one in New Guinea in its vegetation type and structure, climate, soils, etc., but these forests are inhabited by animals, fungi, micro-organisms and plants with very different evolutionary histories. The distribution of organisms among the world's biogeographic realms has been influenced by the distribution of

landmass A landmass, or land mass, is a large region or area of land that is in one piece and not noticeably broken up by oceans. The term is often used to refer to lands surrounded by an ocean or sea, such as a continent or a large island. In the fiel ...

es, as shaped by

plate tectonics Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

over the geological history of Earth.

Concept history

The "biogeographic realms" of Udvardy were defined based on taxonomic composition. The rank corresponds more or less to the floristic kingdoms and zoogeographic regions. The usage of the term "ecozone" is more variable. Beginning in the 1960s, it was used originally in the field of

biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. "Biostratigraphy." ''Oxford Reference: Dictionary of Biology ...

to denote intervals of geological

strata In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...

with fossil content demonstrating a specific ecology. In Canadian literature, the term was used by Wiken in macro-level land classification, with geographic criteria (see Ecozones of Canada). Later, Schultz would use it with ecological and physiognomical criteria, in a way similar to the concept of

. In the

Global 200 The Global 200 is the list of ecoregions identified by the World Wide Fund for Nature ( WWF), the global conservation organization, as priorities for conservation. According to WWF, an ecoregion is defined as a "relatively large unit of land or w ...

/WWF scheme, originally the term "biogeographic realm" in Udvardy sense was used. However, in a scheme of

BBC The British Broadcasting Corporation (BBC) is a British public service broadcaster headquartered at Broadcasting House in London, England. Originally established in 1922 as the British Broadcasting Company, it evolved into its current sta ...

, it was replaced by the term "ecozone".

Terrestrial biogeographic realms

Udvardy biogeographic realms

WWF / Global 200 biogeographic realms

The

World Wildlife Fund The World Wide Fund for Nature (WWF) is a Swiss-based international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the ...

scheme is broadly similar to Miklos Udvardy's system, the chief difference being the delineation of the Australasian realm relative to the Antarctic, Oceanic, and Indomalayan realms. In the WWF system, the Australasia realm includes

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

, the islands of

Wallacea Wallacea is a biogeography, biogeographical designation for a group of mainly list of islands of Indonesia, Indonesian islands separated by deep-water straits from the Asian and Australia (continent), Australian continental shelf, continental ...

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...

, the East Melanesian Islands,

New Caledonia New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a Overseas France#Sui generis collectivity, ''sui generis'' collectivity of t ...

, and

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. Udvardy's Australian realm includes only Australia and Tasmania; he places

in the Indomalayan Realm, New Guinea, New Caledonia, and East Melanesia in the Oceanian Realm, and New Zealand in the Antarctic Realm. The

Palearctic The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa. Th ...

and

Nearctic The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface. The Nearctic realm covers most of North America, including Greenland, Central Florida, and the highlands of Mexico. The parts of North America ...

are sometimes grouped into the Holarctic realm.

Morrone biogeographic kingdoms

Following the nomenclatural conventions set out in the International Code of Area Nomenclature, Morrone defined the next biogeographic kingdoms (or realms) and regions: * Holarctic kingdom Heilprin (1887) ** Nearctic region Sclater (1858) ** Palearctic region Sclater (1858) * Holotropical kingdom Rapoport (1968) ** Neotropical region Sclater (1858) ** Ethiopian region Sclater (1858) ** Oriental region Wallace (1876) * Austral kingdom Engler (1899) ** Cape region Grisebach (1872) ** Andean region Engler (1882) ** Australian region Sclater (1858) ** Antarctic region Grisebach (1872) * Transition zones: ** Mexican transition zone (Nearctic–Neotropical transition) ** Saharo-Arabian transition zone (Palearctic–Ethiopian transition) ** Chinese transition zone (Palearctic–Oriental transition zone transition) ** Indo-Malayan, Indonesian or Wallace's transition zone (Oriental–Australian transition) ** South American transition zone (Neotropical–Austral transition)

Freshwater biogeographic realms

The applicability of Udvardy scheme to most freshwater taxa is unresolved. The

drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

s of the principal oceans and seas of the world are marked by continental divides. The grey areas are

endorheic basin An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent ...

s that do not drain to the ocean.

Marine biogeographic realms

According to Briggs and Morrone: According to the WWF scheme:

References

{{Biomes Biogeography Habitat